The present invention relates to address search systems, and more particularly an address search system for an optical disk player.
An optical disk player is designed so that a light beam is applied to the data recording surface of a recording disk, and a pickup for detecting the recorded data using, for instance, the light beam reflected from the recording surface of the disk is employed to reproduce the data recorded on the disk. The disk player includes as essential components a focus servo device for controlling the position of the convergent point of the light beam emitted from the pickup to form a data detecting light spot on the data recording surface of the disk and a tracking servo device for causing the light spot to follow the spiral recording track formed on the recording surface of the disk.
For the optical recording disk player, an address search system has been proposed in which the present address is compared with a target address, and the data detecting light spot is caused to jump a distance determined according to the difference between the two addresses. A track jumping operation is repeatedly carried out until the target address is reached. In this system, the distance of movement of the light spot in the track jumping operation is detected according to a track pulse formed according to the level of the error signal of the tracking servo device. In this arrangement, if the focus servo control is disrupted, for example, due to scratches on the disk or an external impact, the level of the tracking error signal is decreased and no track pulse is produced.
Accordingly, the conventional address search system is disadvantageous in that the distance of movement of the light spot in the track jumping operation is often detected with error, as a result of which the light spot is positioned away from the target address. At the worst, it can even be moved out of the signal area of the disk. That is, overrun or runaway of the pickup can be caused, resulting in a decrease in access speed, search error, or the suspension of the data reproducing operation.